Breast cancer remains the major cause of cancer death in women with 2015 having ~230,000 new cases diagnosed and 40,000 deaths. The majority of breast cancers (~80%) are invasive ductal cancers (IDC). Invasive lobular cancer (ILC) is the second most common histological subtype of breast cancer, accounting for ~10%-15% of all breast cancers (~24-34,000 annually), and ranks alone as the 8th most common cancer in women. Although the incidence of IDC has remained relatively constant over the last two decades, there has been a significant increase in the number of cases of ILC. Despite showing better prognostic and predictive factors (e.g. more often ER+/PR+, and lower levels of the proliferation marker Ki67), patients with ILC have worse long-term outcome compared to IDC. Unfortunately, both clinical and laboratory studies of breast cancer have focused almost exclusively on IDC, giving little understanding of the unique nature of ILC and causing ILC therapies to be identical to IDC. A recent spate of studies focusing on ILC itself has highlighted unique clinical and biological differences. For example, patients with ILC show a different response to endocrine treatment. Recent studies, for example through The Cancer Genome Atlas (TCGA) ILC working group, have unequivocally shown that ILC has unique biological properties, compared to IDC, however, there is limited understanding of the underlying biology. There has never been a focused meeting to discuss basic, translation, and clinical research on ILC. This R13 application is a request for funding to support the first comprehensive scientific conference focused on ILC, the ?1st International ILC Symposium?, to be held at the University of Pittsburgh, September 29-30, 2016. There are five objectives of the Symposium; 1) Presentation of novel findings in basic, translational, and clinical research on ILC, 2) Generate an opportunity for experts to interact and collaborate, 3) Provide a forum for trainees to present their findings, and thus support the generation of next generation of scientists and clinicians with a research focus on ILC, 4) Offer a forum for listening to and integration with patient advocates and 5) Broadly disseminate the findings and consensus of the meeting in a peer-reviewed manuscript. The Symposium will include 5 scientific sessions (Pathology, Therapeutics, Epidemiology and Genetics, LCIS to ILC progression, and Primary disease and Metastases), one keynote talk, and sessions for early stage investigator/trainees and advocates. Conference attendees will include physicians, scientists (including early stage investigators), fellows and students, and patient advocates. We are in discussion with two breast cancer journals to publish proceedings of the conference. The meeting will be of the highest scientific quality and will support the mission of NIH and specifically that of the NCI. 1